Validity And Reliability Of A Mobile App For Measuring Bar Velocity In The Bench Press Exercise

Abstract

Velocity based-training (VBT) has been demonstrated to be a valid and useful approach to promote greater neuromuscular adaptations in resistance training (RT). This approach typically requires velocity monitoring during RT sessions for appropriate adaptations. The validity and reliability of a chronometer-based mobile App for RT monitoring in the half-squat exercise have been previously shown with a 10 repetition maximum (RM) load, when compared to a linear encoder. However, no data exist with other exercises and different loads. PURPOSE: To determine the validity and reliability of a chronometer-based mobile App for velocity monitoring in the bench press exercise with different loads. METHODS: Twenty handball players (23.0 ± 2.6 yrs, 1.76 ± 0.06 m, 79.6 ± 13.0 kg) completed, after 1RM determination, 5 repetitions with the 25, 40, 55 and 70% of 1RM in the bench press exercise, with the maximal intended velocity, in 2 days separated by 48-72 hrs. Bar velocity (m·s-1) was monitored simultaneously by means of a linear encoder with a sampling rate of 1,000 Hz (reference method), and a chronometer-based mobile App. Validity was examined through paired samples t-test, the Hedge’s effect size (ES), the Pearson’s correlation coefficient (r), and the standard error of estimate (SEE). Reliability was assessed by the coefficient of variation (CV) and the standard error of measurement (SEM). RESULTS: Regarding validity, all relative loads evaluated demonstrated significant differences (P < 0.05) and small to moderate ES (range: 0.31-1.19) between devices, with the mobile App exhibiting greater bar velocities than the linear encoder. However, bar velocities measured with both devices were highly correlated (r ≥ 0.74) with a very low SEE (≤ 0.09 m·s-1). The App exhibited for all loads a low SEM (≤ 0.11 m·s-1), and acceptable CV (< 10%) with the exception of the highest load (70%1RM) (CV = 12.1%). CONCLUSIONS: A chronometer-based mobile App may be considered a valid and reliable method for VBT monitoring in the bench press exercise.